A shutter assembly comprises a rectangular frame, consisting of a pair of vertically opposed side rails and a pair of horizontally opposed side rails, and a plurality of vertically spaced horizontal louvres. When a shutter assembly is not in use, it is swung on hinges around its vertical axis to an open position away from a window or a doorway to give free access to them. When a shutter assembly is in use, the shutter assembly is swung around its vertical axis to a closed position in a window or a doorway. There is a need for a mechanism that holds a shutter assembly in a closed position when the shutter assembly is swung into a window or a doorway. This need may be addressed by providing a latch mechanism incorporated into the vertically opposed side rails of the shutter assembly frame and a catch plate located on at least one of the upper and lower window-sills. When the latch mechanism locks in the catch plate, the shutter assembly is held in a closed position. When the shutter assembly is swung open, the latch mechanism is released from the catch plate and the shutter assembly can be swung around its vertical axis to an open position. Such a latch mechanism and a catch plate for a shutter assembly should have a clean, uncluttered appearance and should be a mechanism that is relatively simple to construct.